What Is Iodine And why should vegans be aware of it?

vegan iodine guide

Iodine is another essential nutrient found abundantly in the earth’s crust, the vast oceans covering the land and is one of the 9 nutrients needed to master the vegan diet. 

Unlike iron with is the most common element by mass found in the earth’s crust, iodine is on the opposite end being the 61st most common element making it a pretty rare element indeed and highlighting its importance due to rarity.

In humans, up to 80% of iodine is found and stored in the thyroid gland but can also be found in muscle tissue, fat cells, and our skin.  

A sufficient iodine supply is paramount to the production of thyroid hormones and since.

Thyroid hormones are used to balance your metabolism and have an effect on nearly all cells in the body so the importance of this rare earth element should not be overlooked.

benefits of iodine

Benefits of Iodine

Since healthy iodine levels are directly linked to healthy thyroid function iodine ends up being inadvertently tied to the prevention of all issues that can occur from an unstable thyroid

  • Overactive thyroid. 1
  • May help to lower the risk of Thyroid cancer. 2
  • Goiter reduction. 3,4
  • Healthy brain development and neurological function. 5,6
  • Healthy childbirth weight. 7,8.
  • Can help with fibrocystic breast disease. 9,10,11.
  • Has been shown to help prevent breast cancer. 12.

Forms of Iodine

Elemental Iodine

  • Elemental iodine consists of 2 iodine atoms I2
  • is unsafe for human use in this form due it’s toxicity 
  • Iodine likes to be bound to other elements and is rarely found naturally on its own.
  • It is mainly found as a salt in the form of an iodide


  • Iodide is formed after binding to another element, mainly potassium or sodium
  • Iodide is safe for human use and consumption
  • All iodine found in the plant is of the bound form iodide, and this is the form you will find in fruit and veg, seaweed and iodized salts

TLDR: The best form of iodine for vegans is an iodide or molecular iodine bound to potassium or sodium

Are vegans more at risk of iodine deficiency than meat-eaters?

To answer this accurately, we need to analyze if there are any high iodine plant-based food sources, how much iodine is required in order to avoid deficiency and if there are any conflicting nutrients that may prevent iodine absorption on a vegan diet

What are the best vegan sources of iodine?

In the typical western diet, the primary sources of iodine tend to come from fish, dairy, eggs, and table salt.

The plant-based foods with the highest source of iodine for vegans are seaweed since they absorb a lot of iodine from seawater.

Seaweed (algae) that contain high levels of iodine

  • Wakame
  • Nori 
  • Arame
  • Kelp
  • Kombu
  • Hiziki 
  • Due to seaweed being highly random in its iodine levels it’s not a reliable way to consistently manage your iodine supply unless measured out accurately in a supplemental form

What about iodine in fruits and vegetables?

The amount of iodine found in fruit and vegetables is largely dependent on the soil that they grow in which makes it hard to determine consistent numbers for iodine in plant-based foods.

Below are some plant-based foods and their Iodine amounts according to the FDA

  • 2 slices of enriched bread = 45 mcg 30% RDA
  • Fruit cocktail in syrup (½ cup) = 42mcg 28% RDA
  • 5 dried prunes = 13mcg 9% RDA
  • Raisin bran cereal (1 cup) = 11mcg 7% RDA
  • Lima beans boiled (½ cup) = 8mcg 5% RDA
  • Green peas boiled (½ cup) = 3mcg 2% RDA
  • Banana (1 medium) = 3mcg 2% RDA

Iodized salt

Iodized salt is simply salt mixed with iodine

In some countries, iodine has been added to table salt creating iodides formed with sodium which have been used as a way to prevent iodine deficiencies on a wide scale

Research has shown that consuming 150-200 mcg iodine per day may help to improve iodine levels over time.

There is around 45 mcg of iodine in every gram of iodized salt

So to hit the RDA of 150- 200mcg you would need around 3-5 grams of iodized salt daily

Iodine supplementation

plant-based iodine supplementaion

Iodine supplementation is a great way for vegans who don’t want to use iodized salt as a primary source of iodine due to the effects that excess salt can have on your system. For the vegans and vegetarians who do not want to have to rack their brains too much on managing levels of iodine in their daily food schedule or for those who simply do not want seaweed and salt in their diets an iodine supplement is a good alternative

The main forms of iodine you want to look out for in supplementation are potassium iodide and sodium iodide with a product that can provide around 150mcg per serving. 

So how much iodine do vegans need?

The average recommended amount for vegan and non-vegan adults is 150-200µg dependant on your country

Different countries have different recommended amounts for iodine

  • Germany and german-speaking countries 200 µg/day for adults
  • These number change as you get above 51 years of age to 180 µg/day
  • Switzerland recommends 150 µg/day. The recommended amount does not change with age and stays stationary at 150 µg/day 
  • The UK recommends at least 0.14mg or 140µg of iodine a day
  • The US recommended intake is 0.15mg or 150µg of iodine a day

*µg= micrograms. There are 1000 micrograms in a milligram*

Unlike other nutrients where you are advised to intake more as you age the general consensus from the majority of countries is to maintain iodine levels of 150-200 micrograms into old age

TLDR: 150-200µg is a safe range for vegans and non-vegans alike

Other factors that can affect how much iodine we need

We usually lose iodine through everyday human processes such as sweat, excretion & urination or bleeding but being aware of the other factors that can affect iodine absorption or loss is important to stay healthy into the future. 

iodine absorption

Iodine absorption factors include:


Iodine plays a critical role in healthy child growth and development

A relatively high amount of iodine is needed in the first year of birth at around 110-130mcg. During the ages of 1-3, the amount required slightly drops to around 90mcg, and as we get old the required amount continues to rise, peaking at around 150mcg during the end of puberty. This amount stays relatively stable through adulthood and into old age.


During pregnancy, the iodine requirements for the mother are increased by up to 50% so for those unaware of the increased iodine requirements they may be more susceptible to iodine deficiency

Sufficient iodine is crucial to healthy child development in the womb and in early life so maintaining a healthy iodine balance is very important

Environmental chemicals

  • Perchlorates
    • High levels of perchlorates can block iodine absorption and cause thyroid issues
    • Found in fireworks, flares, and matches
    • Can be found in soil and fertilizers 
    • It can also be found in dairy especially cows milk if the plants the cows eat from has perchlorates in the soil or the water they drink from has been contaminated. 
  • Thiocyanates
    • Similar to perchlorates high levels of thiocyanates can also block iodine absorption and cause thyroid issues 
    • Found in cigarette smoke  
    • Found in cruciferous vegetables to a small degree but not in dangerous amounts
    • Lowering exposure to these chemicals will overall help to increase iodine uptake.


Alcohol use has a direct effect on the suppression of thyroid function due to causing significant toxicity on the cellular level.


Exposure to radiation can affect the functionality of the thyroid.

The use of stable iodine in the case of radiation exposure may help to restore thyroid function.


Since iodine deficiency has a direct effect on thyroid function and thyroid function affects energy, and a multitude of cellular processes, it is safe to say having an insufficient supply of iodine can affect athletic performance.

Iodine lost through sweat during exercise may have adverse effects on thyroid function if not balanced through dietary intake.

Studies have shown up to 52 mcg of iodine can be lost through 1 hour of exercise which make those who sweat a lot more prone to iodine loss and thyroid issues.

Based on the research it appears evident that those partaking in regular intensive exercise are more susceptible to iodine deficiency so making sure to manage dietary iodine effectively is vital to prevent future problems

Iodine deficiency vs excess

iodine deficiency

Iodine deficiency

Since iodine plays such an important part in so many of our bodily functions, it is crucial to be aware of some of the symptoms that could be linked to a possible iodine deficiency. 

If you notice any of these signs consult your doctor for advice

  • Some symptoms to look out for:
    • Excess weight gain. 12,  
    • Neurological issues. 3.
      • Memory and learning issues. 4,5.
      • Reduced brain development. 6.  
      • Underdeveloped growth and brain development during pregnancy. 7.
    • Tiredness and low energy. 8. 
    • Weak hair and dry skin. 9,10
    • Abnormal temperature fluctuations and higher sensitivity to the cold. 11,12

Can you have too much iodine in your diet?

Iodine is a relatively safe nutrient with a high upper intake limit and those that are more susceptible to having issues with excess iodine tend to be people who already have a dysfunctional thyroid.

Iodine upper intake limits for adults according to the National Academy of Sciences, Engineering and Medicine is 1,100 ug a day

The upper intake limits for children, teenagers, and women going through pregnancy vary. Data is shown below for reference

  • Upper intake limits (general)
    • 1-3 years of age = 200µg of iodine a day 
    • 4-8 years of age = 300µg of iodine a day 
    • 9-13 years of age = 600µg of iodine a day 
    • 14-18 years of age = 900µg of iodine a day 
    • 19 and above = 1100µg of iodine a day 
  • Upper intake limits (pregnancy & lactation)
    • 14-18 years of age = 900µg of iodine a day 
    • 19-50 years of age = 1100µg of iodine a day 
  • Data reference from the National academies of Sciences, Engineering and Medicine 

Symptoms of excess Iodine are rare but look out for signs of

*If you notice any symptoms consult your doctor for advice*

TLDR: General take away from the research is to stick within the healthy recommended range of 150-200µg per day unless otherwise advised by your doctor. Exceeding the 150-200µg doesn’t appear to cause any significant issues but staying under the upper limit of 1100µg appear to be the best course of action in the majority of situations

The only situations that may require more iodine than the upper limit of 1100µg are in severe iodine deficiency cases or when trying to treat fibrocystic breast disease.

*always consult your doctor before deviating from the RDA*

Minerals and vitamins that can affect iodine absorption

Nutrients that can increase iodine absorption

  • Selenium 
  • Magnesium
    • Maintaining a healthy dose of dietary magnesium appears to be vital to efficient iodine uptake since studies have shown supplementing magnesium can increase overall iodine absorption
    • Foods high in magnesium
      • Spinach, pumpkin seeds, lima bean, and brown rice
  • Vitamin C 
    • A recent study on iodine intake has shown that increasing vitamin c can improve the overall uptake of Iodine
    • Foods high in vitamin C
      • Guavas
      • Bell peppers
      • Kiwi fruit
  • Vitamin A
    • Like selenium, vitamin A combined with iodine has been shown to work synergistically in helping to reduce thyroid issues 
    • Foods high in vitamin A
      • Carrots
      • Butternut squash
      • Cantaloupe 

TLDR: Maintaining a healthy dietary supply of selenium, magnesium, vitamin a and vitamin c can help support iodine in healthy thyroid function and maintenance

Nutrients that can decrease iodine absorption


  • Goitrogens which are natural plant pesticides can prevent efficient iodine uptake potentially leading to thyroid issues
  • They are mainly found in cruciferous vegetables, some starchy vegetables, and soy products
  • List of vegetables with higher levels of goitrogens
    • Broccoli
    • Cauliflower
    • Kale
    • Brussel sprouts
    • Cassava
    • Sweet potato
    • Tofu
    • Soy milk
  • Although vegetables contain goitrogens that can prevent iodine uptake, it’s not usually an issue for healthy individuals
  • Studies have shown that increasing potassium iodide through iodized salts or iodine supplementation has been shown to help reverse the effects of goitrogens but those who already have thyroid issues need to be careful of consuming goitrogenic foods
  • Cooking goitrogenic foods also reduces goitrogen levels by up to 90%


When comparing the amount of high iodine food sources in a typical vegans diet vs the amount in a non-vegans standard diet, it’s easy to see that due to lower amount of reliable options vegans can become more susceptible to iodine issues, mainly if seaweeds (the plant-based source with the highest iodine content) are not used regularly. 

The levels of iodine in a food source are highly dependant on the levels of iodine in the water or soil that the food was grown or raised in. 

Due to iodine being highly abundant in the oceans and seaweed/algae, fish will always be a reliable source of iodine for non-vegans, but the reliability of iodine in the soil is harder to quantify due to the multitude of ways that soil can be affected. 

Another potential spanner in the works for vegans are goitrogens which prevent iodine uptake and are found in quite a few plant-based foods

But as the research shows all is not lost since the solutions for vegans are actually pretty simple

As with most nutritional issues regarding plant-based eating, they tend to stem from a lack of knowledge on what to do and what foods to eat to maintain a healthy balance of nutrients on a day to day basis.

In the case of iodine, vegans need to make sure they gain the correct knowledge of which plant-based foods are consistently higher in iodine and make them regular staples in their diet

Some easy way to incorporate more iodine into your diet are:

  • Sprinkling seaweed on your favorite stir fry vegetable dish
  • Having a regular helping of dried prunes throughout the day
  • Consuming fortified bread
  • Using iodized salt
  • Or simply buying a healthy plant-based iodine supplement and taking it daily

The aim with these options is to hit the RDA of 150-200 mcg and stay under the upper intake limit of 1100 mcg unless otherwise stated by your doctor

Combining these simple steps with your new-found knowledge of all the ins and outs related to iodine should hopefully have given you the tools and confidence to create healthy nutritional balance in your life and should have you well on your way to becoming a benevolent master of the plant-based diet


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